The present invention relates generally to porous ceramic articles and methods for producing the same, and particularly to methods of producing porous ceramic articles using an organic hydrogen peroxide as the pore forming agent.
Porosity in ceramic substrates has been generated for decades by the use of organic pore formers. Typical organic pore formers such as graphite, starch, rice and cork have a large exotherm from 400-900° C. This exotherm results in cracking issues during calcination and very slow ramp rates. Organic pore formers typically produce a ceramic substrate with between 50% and 60% porosity. As the market pushes forward the demand for low cost and high porosity ceramic substrates continues. To achieve high porosity from conventional organic pore formers, a large amount of material must be added. Sometimes greater than 50% organic pore former was needed to achieve 65% porosity. In addition, for high porosity demands, this larger organic pore former loading does not produce equivalent resulting porosity.
Recently, hydrogen peroxide has been used to generate porosity in alumina titanate bodies. While overcoming the disadvantages of the conventional “burn out” pore formers, hydrogen peroxide was not optimal. Ceramic oxides catalyzed hydrogen peroxide on contact, resulting in changing porosity through extrusion and drying. Ultimately, the last piece extruded and dried had a much larger porosity than the first piece extruded.
Therefore it would be desirable to have a pore forming agent that provided ceramic substrates having more consistent and greater porosity, that could be controlled to give a desired pore size and would not require a “burn out” period. It would also be advantageous if such a pore former were not catalyzed upon contact with ceramic oxides, but was stable through an extrusion or molding step.